A. Field of the Invention
The present invention pertains generally to life safety systems such as boilers, furnaces, hot water heaters, etc. and more specifically to the components for controlling these systems, such as actuators and controllers.
B. Background of the Invention
Combustion systems, such as a system that modulates the fuel/air ratio of large burner, require preventive measures that guard against alteration of the system. For example, fuel/air control systems are used on modulating burners that fire boilers to produce steam or hot water for process and/or heating applications.
Different types of combustion systems, and even combustion systems of the same genre, typically operate in the most efficient and safest manner with fuel/air profiles that are specifically configured for that particular system. In large commercial applications, it is not uncommon to have multiple and dissimilar combustion systems at the same location and possibly in near proximity. Various systems components, such as fuel/air controllers, or actuators, may fail over time. A common troubleshooting technique, especially in emergency situations, is to utilize or swap components from another system or obtain components from a service technician. The response characteristics of the actuators can vary greatly from component to component. For example, the initial starting position of a particular actuator may vary from model to model and its response characteristics to current control signals may be different. Similarly, different fuel/air controllers typically provide profiles that are completely different from the profile that was recorded during the initial setup (initial configuration or initial commissioning).
These problems may significantly affect the operation of the combustion system. For example, the swapping of a fuel/air controller may result in the use of a fuel/air controller that has an invalid light-off position. The curve programmed into the new fuel/air controller may introduce a fuel rich atmosphere into the combustion chamber which can become explosive or cause stack fires. Similarly, the fuel/air controller may not be designed to provide sufficient purge prior to lighting. Lean fuel conditions can also cause problems associated with the flame front leaving the burner head. This creates a region of unburned fuel which can re-ignite or flame out. Any of these situations can result in property loss, injury and even death.
The swapping of actuators can result in similar problems. This is because there is not any method to ensure that the replacement actuator is attached to the shaft at the same exact positional relationship as the actuator that was configured or commissioned with the combustion system. Moreover, the actual response of the actuator to current values may vary from the original actuators.
At least one previous method of preventing the replacement of a component has used expensive microswitches that are placed on the back of the component so that when the component is lifted from its subbase, the component is inactivated. Such systems require expensive batteries and battery monitoring circuits to ensure that they are operational. Further, such systems are not forgiving in cases of routine maintenance or initial troubleshooting due to wiring errors that require the component to be removed.
Hence, it is desirable to have a system in which replacement of either controllers or actuators cannot be accomplished without reconfiguring or recommissioning the controller with the appropriate combustion profile for the particular components involved.